A head-wearable or head-mounted display (“HMD”) is a display device worn on or about the head. HMDs usually incorporate some sort of near-to-eye optical system to display an image within a few centimeters of the human eye. Single eye displays are referred to as monocular HMDs while dual eye displays are referred to as binocular HMDs. Some HMDs display only a computer generated image (“CGI”), while other types of HMDs are capable of superimposing a computer generated image (“CGI”) over a real-world view. This latter type of HMD is often referred to as augmented reality because the viewer's image of the world is augmented with an overlaying CGI, also referred to as a heads-up display (“HUD”).
One goal of designing HMDs is to have the device disappear from an observer point of view. Conventional HMDs are implemented with a light source that emits display light initially having a cone of divergence. In order to bring this display light into focus in a near-to-eye configuration, optics are used to collimate or nearly collimate this divergent light. These optics are typically implemented using one or more reflective, refractive, or diffractive lenses. These conventional optical elements typically must tradeoff bulk and size with field of view, eyebox, and spectral bandwidth.
HMDs have numerous practical and leisure applications. Aerospace applications permit a pilot to see vital flight control information without taking their eye off the flight path. Public safety applications include tactical displays of maps and thermal imaging. Other application fields include video games, transportation, and telecommunications. Due to the infancy of this technology, there is certain to be new found practical and leisure applications as the technology evolves; however, many of these applications are limited due to the cost, size, field of view, and efficiency of conventional optical systems used to implement existing HMDs.